Incomplete self-similarity and fatigue-crack growth

Ritchie, Robert O.

doi:10.1007/s10704-005-2266-y

Cited by 75 publications

(53 citation statements)

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“…2). The values of the critical scale l sc for various stages of crack propagation are presented in the table.Manifestations of the self similar nature of the fatigue crack growth were studied using methods of the theory of similarity and dimensionality [6,7]. The crack growth rate was defined as a = dl/dN (where l is the crack length and N is the number of cycles) and studied as for correlation with the following parame ters: a 1 = ΔK, stress intensity coefficient; a 2 = E, Young's modulus; a 3 = l sc , correlation scale in the ensemble of defects; a 4 = L pz , the scale related to the process zone.…”

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confidence: 99%

Scaling invariance of fatigue crack growth in gigacycle loading regime

et al. 2010

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible.This is an author-deposited version published in: http://sam.ensam.eu Handle ID: .http://hdl.handle.net/10985/10516To cite this version :V. OBORIN, M. BANNIKOV, O. NAIMARK, Thierry PALIN-LUC -Scaling invariance of fatigue crack growth in gigacycle loading regime -Tech. Phys. Lett. -Vol. 36, n°11, p.1061-1063 -2010 Any correspondence concerning this service should be sent to the repository Administrator : archiveouverte@ensam.euThe task of assessing the working resource of important structures, in particular, those for aircraft engines, poses qualitatively new basic problem related to evaluation of the reliability of materials under con ditions of cyclic loading in excess of 10 6 -10 10 cycles, which refer to the field of so called gigacycle fatigue. This interest is related to the fact that the resource of loading for many important parts operating under conditions of cyclic loading exceeds the so called multicycle range. the behavior of materials in the range of gigacycle fatigue reveals some qualitative changes in the laws governing both the nucleation of cracks (in the bulk of a sample) and their propagation, which are related to changes in the mechanisms of fatigue crack nucleation and propagation. In the range of gigacycle loading, the fatigue curve exhibits discon tinuities and the behavior shows evidence of a signifi cant increase in the role of environment, so that the problem acquires an interdisciplinary character.The stages of material fracture in the range of giga cycle loading are classified based on the structural signs of damage related to a broad spectrum of spatial scales, including persistent slip bands (PSBs), fatigue striations, microcracks (formed as a result of PSB crossing), and grain boundary defects. The main damage refers to the defect scales within 0.1 μm-1 mm, which are significantly smaller than those detected by the standard methods of nondestructive testing used for the conventional monitoring of reli ability, in particular, during the exploitation of build ings.An effective method for investigating the role of initial structural heterogeneity, monitoring the accu mulation of defects on various scales (dislocation ensembles, micropores, microcracks), and determin ing critical conditions for the transition from dispersed to macroscopic fracture is offered by the quantitative fractography. This technique reveals the characteristic stages of fracture (crack nucleation and propagation), thus providing a base for evaluating the temporal resource of materials and structures under conditions of gigacycle loading.The approach to characterization of the fracture surface morphology in terms of spatiotemporal invari ants was originally proposed by Mandelbrot [1]. This method is based on an analysis of the relief of a frac ture surface, which exhibits the property of self affin ity as manifested by the invariant characteristics of the surrace re...

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Scaling invariance of fatigue crack growth in gigacycle loading regime

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“…If in addition to the fatigue mode (striations) ductile tearing occurs (e. g. dimples), crack propagation is accelerated and the slope m shall increase [15,16].…”

Section: (2010) 11-12mentioning

confidence: 99%

“…Small width specimens have been used in the literature [19,20], but how these fatigue crack propagation data correlate with those of large width specimens has not been commented. Thus, questions on validity and equivalency of data due to the size effect cannot be excluded when variations in the fracture mode [14][15][16] are likely to occur.…”

Section: (2010) 11-12mentioning

confidence: 99%

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Vaidya¹,

Horstmann²,

Angamuthu³

et al. 2010

Materials Testing

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Accuracy of indirect fatigue crack length measurement by potential drop method or by compliance technique may be affected at low load ratio due to fracture surface contact, crack closure or mixed mode fracture. As an alternative, the maximum value of crack opening displacement, CODmax, from a clip gauge was utilized. Middle crack tension M(T) specimens were used to obtain conservative data at a low load ratio (R = 0.1). Thin sheet specimens (B = 3.2 mm) with different widths (100 mm ≤ W ≤ 400 mm) of AA6056-T4 were investigated in the mid-regime (Paris regime), which is of interest for damage tolerance analysis. The use of CODmax is found to provide crack lengths equivalent to those measured optically. Hence, the method is very suitable for indirect crack length measurement. Furthermore, small width specimens provided data equivalent to large width specimens. Insofar, the size effect is found to be absent, and fatigue crack propagation data can be acquired on small width specimens when material availability is limited.

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“…Botvina, processing the data by Heiser and Mortimer [33] (see [32]), and R.O. Ritchie [34], processing the data by Knott and Ritchie [35] (Figures 7 and 8), showed that the dependence of m upon Z, i.e., upon the specimen size can be substantial. Therefore, using in practical structural design of the results of the standard fatigue experiments performed on small specimens can be dangerous: the real life-time of the structure can be overestimated.…”

Section: Paris Law -An Example Of Incomplete Similaritymentioning

confidence: 99%

Scaling Phenomena in Fatigue and Fracture

Баренблатт

2006

Int J Fract

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The general classification of scaling laws will be presented and the basic concepts of modern similarity analysis -intermediate asymptotics, complete and incomplete similarity -will be introduced and discussed. The examples of scaling laws corresponding to complete similarity will be given. The Paris scaling law in fatigue will be discussed as an instructive example of incomplete similarity. It will be emphasized that in the Paris law the powers are not the material constants. Therefore, the evaluation of the life-time of structures using the data obtained from standard fatigue tests requires some precautions.

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Incomplete self-similarity and fatigue-crack growth

Cited by 75 publications

References 20 publications

Scaling invariance of fatigue crack growth in gigacycle loading regime

Scaling invariance of fatigue crack growth in gigacycle loading regime

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Scaling Phenomena in Fatigue and Fracture

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Incomplete self-similarity and fatigue-crack growth

Cited by 75 publications

References 20 publications

Scaling invariance of fatigue crack growth in gigacycle loading regime

Scaling invariance of fatigue crack growth in gigacycle loading regime

Utilising CODmax as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Scaling Phenomena in Fatigue and Fracture

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Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056